1. Technical Field
The disclosure relates generally to semiconductor fabrication, and more particularly, to methods of using a metal mask and converting it to a metal oxide etch stop layer, and a related semiconductor structure.
2. Background Art
Middle-of-line (MOL) fabrication during semiconductor device manufacture includes operations performed on the semiconductor wafer during and following first metallization. Current MOL processing includes using an etch stop layer (ESL) that is deposited and then selectively etched/opened. The openings in the ESL are then used to control critical dimensions (CDs) of contacts to an active region. The active region includes a number of semiconductor devices, e.g., transistors, to which the contacts are electrically coupled. This approach to control contact CDs is complicated because the ESL material is often difficult to etch, thus making controlling the CDs more difficult. Metal hard masks are not a viable solution because the conductive metal film cannot exist at each level for operability issues, and thus must be removed at each level.